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If you use a flow hood you will be able to see the amount of cfms coming out of each register. Lets see if you are close to 1400-1600 cfms. Do the right test now that the leakage is fixed. This will also tell you if your existing system can handle the new equipment. What is the static pressure? We want to find out the total amount of air you are moving at a particular static pressure. .05?, 08?, 1.?

You are not done testing. You could have a perfect duct system, but it may only handle half the cfms YOU need.

I've been all over the web reading about install issues where the tech forgot something and the callback tech couldn't find it, so it took months of frustration for the homeowner to get it resolved.

Bingo. Nicely put. This is not just dip issues, often it's design.

Communicating equipment don't need dip switches. You get how people didn't get calculators when you were on to computers, that's where hvac equipment is now. Equipment using dips is 1980s tech, communicating equipment is like an iPad.

Your '4 ton air handler' is likely set to 3-3.5 ton of airflow, 1200-1400 cfm. 4 ton will be set 200 cfm higher, so we can be fairly certain that's a bad idea. Be nice to know airflow, which can be backed into by knowing fan setting and measuring static. .5 is too high.

If you have a 1 gallon jug and 1.2 gallons of milk, you'll always be wasting milk. Ideally you have excess capacity in your jug. .3 static seems to be a number I associate with happy homeowners, very quiet systems, and surprisingly low bills.

If you use a flow hood you will be able to see the amount of cfms coming out of each register. Lets see if you are close to 1400-1600 cfms. Do the right test now that the leakage is fixed. This will also tell you if your existing system can handle the new equipment. What is the static pressure? We want to find out the total amount of air you are moving at a particular static pressure. .05?, 08?, 1.?

You are not done testing. You could have a perfect duct system, but it may only handle half the cfms YOU need.

The FPL rep who did the duct test didn't leave me with any of the readings. She said there was leakage at each register and left me the $ rebate certificate for the repair work, along with a diagram of register locations that required sealing. So I don't have any cfm info on the registers, if indeed that's what she was measuring.

How would measuring cfm at each register with the existing equipment (3.5 ton single compressor) determine whether the ductwork could handle new, possibly 4 ton dual compressor?

How does one determine external static pressure (ESP)?

Bottom line question I asked earlier in this thread: Who the h*** does one call to have this type of testing done?

Your '4 ton air handler' is likely set to 3-3.5 ton of airflow, 1200-1400 cfm. 4 ton will be set 200 cfm higher, so we can be fairly certain that's a bad idea.

Huh? What's a bad idea? My thought was that measuring cfm is useless (a bad idea) in evaluating ductwork capacity for handling a new 4 ton dual compressor system because my 4 ton air handler is likely set to a lower cfm to match the condenser. Is that what you meant by bad idea?

Forgive me, but I can be a little dense at interpreting cryptic comments. lol

Fla Joy, here's the deal.
Different models are made for the wide variety of homes, environments, regions, and personal preferences.

With that said, there are better logical choices for your home, and there are other more satisfying choices.

Do we need designer clothes? No, but do you walk into an important meeting room with a Walmart suit on, sneakers and a baseball cap?

I have customers ask me daily, "how much money will the high end save me in utilities compared to the basic?"
I tell them the truth, technically if you go by SEER rating alone, you will never recoup the investment difference. However, as I stated earlier, there are different models to fit different needs. In certain cases, YES an XL20i can prove to be an excellent choice, and may even give you that redemption through your utility bills.

Your neighbors home may have different needs. For instance, maybe his kids are out of the house, and your children are at home all day with Mom. You may have pets which increase the need for filtration. He may have a gigantic heated fish tank. You may have a 70" plasma, he may not watch tv. He may have a simple 2 story, you have two story with a room over garage and sun room.

With that said, you need to look at your own situation, and the needs you want satisfied. For someone like yourself doing so much research, it's difficult to imagine you being happy with a standard builders grade unit.

You need to narrow your choice down to a single contractor. One that you trust is giving you the correct information. If you play the numbers game with several contractors, you're going to end up with what you pay for.

If you have a two story and want zoning, you would be silly not to install an XL20i. If you have a 1000sqft ranch you would be silly to install an XL20i. (certain exceptions excluded)

Why do many contractors dismiss ducting issues? It's simple, there is no money in duct work! I will prove this by asking you how much adding a full duct replacement should cost? (w/o $$ of course?) use a % increase of the cost of the simple unit changeout.

Lastly, if you think you're old Rheem is going to fail permanently at the perfect time, you are silly. Start saving money now. Otherwise you're paying your utility company, as you stress over this decision. Your stress will continue when it fails in the middle of winter when there are no rebates or incentives.

Fla Joy, here's the deal.
Different models are made for the wide variety of homes, environments, regions, and personal preferences.

With that said, there are better logical choices for your home, and there are other more satisfying choices.

Do we need designer clothes? No, but do you walk into an important meeting room with a Walmart suit on, sneakers and a baseball cap?

I have customers ask me daily, "how much money will the high end save me in utilities compared to the basic?"
I tell them the truth, technically if you go by SEER rating alone, you will never recoupe the investment difference. However, as I stated earlier, there are different models to fit different needs. In certain cases, YES an XL20i can prove to be an excellent choice, and may even give you that redemption through your utility bills.

Your neighbors home may have different needs. For instance, maybe his kids are out of the house, and your children are at home all day with Mom. You may have pets which increase the need for filtration. He may have a gigantic heated fish tank. You may have a 70" plasma, he may not watch tv. He may have a simple 2 story, you have two story with a room over garage and sun room.

With that said, you need to look at your own situation, and the needs you want satisfied. For someone like yourself doing so much research, it's difficult to imagine you being happy with a standard builders grade unit.

You need to narrow your choice down to a single contractor. One that you trust is giving you the correct information. If you play the numbers game with several contractors, you're going to end up with what you pay for.

If you have a two story and want zoning, you would be silly not to install an XL20i. If you have a 1000sqft ranch you would be silly to install an XL20i. (certain exceptions excluded)

Lastly, if you think you're old Rheem is going to fail permanently at the perfect time, you are silly. Start saving money now. Otherwise you're paying your utility company, as you stress over this decision. Your stress will continue when it fails in the middle of winter when there are no rebates or incentives.

Forgive me, but your reply made me laugh. I agree with everything you've said, except the thought that I would be stressed if it failed permanently in the middle of winter. The only time I might turn on the heat is if my son's family visits and spends the night. Otherwise, I enjoy the lower inside temps during the winter. About 15 years ago I lived in another home in central Florida and didn't even realize I had oil heat in the house.... I never ever thought to investigate turning on heat! I discovered there was actually a working oil furnace when I decided to move! Of course, I did feel a little stupid not knowing.

The biggest issue I'm having is deciding what WILL satisfy ME, as well as finding that totally trustworthy single contractor you spoke about. I'm actually not playing numbers games between the two contractors, I'm trying to decide which one is more trustworthy.

I plan on starting another thread to address a major difference between the two contractors that concerns me. I won't mention it here so the thread doesn't get "hijacked".

Blower door test doesn't tell you anything about air balance of system. Even a duct blaster won't tell you if your system is balanced.

I don't have "hot spots" or "cold spots". So, to use a medical analagy, if I don't have any of the symptoms of an unbalanced system, why spend the time to locate a professional and pay him to diagnose an ailment that I'm not complaining about?

I don't have "hot spots" or "cold spots". So, to use a medical analagy, if I don't have any of the symptoms of an unbalanced system, why spend the time to locate a professional and pay him to diagnose an ailment that I'm not complaining about?

FORGET EACH ROOM!!!! You have a 3.5 ton system right now, it's working (moving air). Find out the TOTAL cfm the system is pushing RIGHT NOW and at what static pressure it's doing it at. THE TOTAL. If you are pushing 1000 at .8, you will never push 1400 at .05, .08 or .1